System and method for multilevel scheduling

ABSTRACT

A method and apparatus for determining multilevel scheduling of a reverse link communication. An embodiment includes estimating capacity on the reverse link based on the sector load. An embodiment includes estimating load contribution based on an estimated signal-to-noise ratio. An embodiment includes estimating capacity available to schedule based on a ratio of measured other-cell interference over thermal noise, and based on sector load. An embodiment includes a method of distributing sector capacity across a base station (BS) and a base station controller (BSC). An embodiment includes determining priority of a station based on the pilot energy over noise plus interference ratio, the soft handoff factor, the fairness value, and the fairness factor α.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present application for patent is a divisional of patent applicationSer. No. 10/640,720 entitled “SYSTEM AND METHOD FOR MULTILEVELSCHEDULING”, filed Aug. 13, 2003, pending, which claims priority toProvisional Application No. 60/409,820 entitled “SYSTEM AND METHOD FORMULTILEVEL SCHEDULING FOR RATE ASSIGNMENT”, filed Sep. 10, 2002, andassigned to the assignee hereof and hereby expressly incorporated byreference herein.

REFERENCE TO CO-PENDING APPLICATIONS FOR PATENT

The present application for patent is related to the followingco-pending U.S. patent application Ser. No. 10/640,777 by Avinash Jain,entitled “SYSTEM AND METHOD FOR RATE ASSIGNMENT”, filed Aug. 13, 2003,assigned to the assignee hereof and expressly incorporated by referenceherein.

BACKGROUND

1. Field

The present disclosed embodiments relate generally to wirelesscommunications, and more specifically to reverse link rate scheduling ina communication system having a variable data transmission rate.

2. Background

The field of communications has many applications including, e.g.,paging, wireless local loops, Internet telephony, and satellitecommunication systems. An exemplary application is a cellular telephonesystem for mobile subscribers. (As used herein, the term “cellular”system encompasses both cellular and personal communications services(PCS) system frequencies.) Modern communication systems designed toallow multiple users to access a common communications medium have beendeveloped for such cellular systems. These modern communication systemsmay be based on code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA), spacedivision multiple access (SDMA), polarization division multiple access(PDMA), or other modulation techniques known in the art. Thesemodulation techniques demodulate signals received from multiple users ofa communication system, thereby enabling an increase in the capacity ofthe communication system. In connection therewith, various wirelesssystems have been established including, e.g., Advanced Mobile PhoneService (AMPS), Global System for Mobile communication (GSM), and someother wireless systems.

In FDMA systems, the total frequency spectrum is divided into a numberof smaller sub-bands and each user is given its own sub-band to accessthe communication medium. Alternatively, in TDMA systems, each user isgiven the entire frequency spectrum during periodically recurring timeslots. A CDMA system provides potential advantages over other types ofsystems, including increased system capacity. In CDMA systems, each useris given the entire frequency spectrum for all of the time, butdistinguishes its transmission through the use of a unique code.

A CDMA system may be designed to support one or more CDMA standards suchas (1) the “TIA/EIA-95-B Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System” (theIS-95 standard), (2) the standard offered by a consortium named “3rdGeneration Partnership Project” (3GPP) and embodied in a set ofdocuments including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard offeredby a consortium named “3rd Generation Partnership Project 2” (3GPP2) andembodied in “TR-45.5 Physical Layer Standard for cdma2000 SpreadSpectrum Systems” (the IS-2000 standard), and (4) some other standards.

In the above named CDMA communication systems and standards, theavailable spectrum is shared simultaneously among a number of users, andtechniques such as soft handoff are employed to maintain sufficientquality to support delay-sensitive services, such as voice. Dataservices are also available. More recently, systems have been proposedthat enhance the capacity for data services by using higher ordermodulation, very fast feedback of Carrier to Interference ratio (C/I)from a mobile station, very fast scheduling, and scheduling for servicesthat have more relaxed delay requirements. An example of such adata-only communication system using these techniques, is the high datarate (HDR) system that conforms to the TIA/EIA/IS-856 standard (theIS-856 standard).

In contrast to the other above named standards, an IS-856 system usesthe entire spectrum available in each cell to transmit data to a singleuser at one time. One factor used in determining which user is served islink quality. By using link quality as a factor for selecting which useris served, the system spends a greater percentage of time sending dataat higher rates when the channel is good, and thereby avoids committingresources to support transmission at inefficient rates. The net effectis higher data capacity, higher peak data rates, and higher averagethroughput.

Systems can incorporate support for delay-sensitive data, such as voicechannels or data channels supported in the IS-2000 standard, along withsupport for packet data services such as those described in the IS-856standard. One such system is described in a proposal submitted by LGElectronics, LSI Logic, Lucent Technologies, Nortel Networks, QUALCOMMIncorporated, and Samsung to the 3rd Generation Partnership Project 2(3GPP2). The proposal is detailed in documents entitled “Updated JointPhysical Layer Proposal for 1xEV-DV”, submitted to 3GPP2 as documentnumber C50-20010611-009, Jun. 11, 2001; “Results of L3NQS SimulationStudy”, submitted to 3GPP2 as document number C50-20010820-011, Aug. 20,2001; and “System Simulation Results for the L3NQS Framework Proposalfor cdma2000 1x-EVDV”, submitted to 3GPP2 as document numberC50-20010820-012, Aug. 20, 2001. These are hereinafter referred to asthe 1xEV-DV proposal.

Multi-level scheduling may be useful for more efficient capacityutilization on the reverse link.

SUMMARY

Embodiments disclosed herein address the above stated needs by providinga method and system for multilevel scheduling for rate assignment in acommunication system.

In an aspect, a method for estimating capacity used on a reverse link,comprises measuring a plurality of signal-to-noise ratios at a stationfor a plurality of rates, determining sector load based on the measuredplurality of signal-to-noise ratios, an assigned transmission rate, andan expected transmission rate, and estimating capacity on the reverselink based on the sector load.

In an aspect, a method of estimating load contribution to a sectorantenna, comprises assigning a transmission rate Ri on a firstcommunication channel, determining an expected rate of transmission E[R]on a second communication channel, estimating a signal-to-noise ratio ofa station for the assigned transmission rate Ri on the firstcommunication channel and the expected rate of transmission E[R] on asecond communication channel, and estimating the load contribution basedon the estimated signal-to-noise ratio.

In an aspect, a method for estimating capacity available to schedule,comprises measuring other-cell interference during a previoustransmission (I_(oc)), determining thermal noise (N_(o)), determiningsector load (Load_(j)), and determining rise-over-thermal (ROT_(j))based on the ratio of the measured other-cell interference over thermalnoise, and based on the sector load.

In another aspect, a method of distributing sector capacity across abase station (BS) and a base station controller (BSC), comprisesmeasuring other-cell interference during a previous transmission(I_(oc)), determining thermal noise (N_(o)), determining a maximumrise-over-thermal (ROT(max)), determining an estimated assigned load atthe BSC (Load_(j)(BSC)), and determining a sector capacity distributedto the base station based on the ratio of the measured other-cellinterference over thermal noise, the maximum rise-over-thermal, and theestimated assigned load at the BSC.

In yet another aspect, a method of determining priority of a station,comprises determining pilot energy over noise plus interference ratio(Ecp/Nt), determining a soft handoff factor (SHOfactor), determining afairness value (F), determining a proportional fairness value (PF),determining a fairness factor α, and determining a maximum capacityutilization based on the pilot energy over noise plus interferenceratio, the soft handoff factor, the fairness value, and the fairnessfactor α.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 exemplifies an embodiment of a wireless communication system withthree mobile stations and two base stations;

FIG. 2 shows set point adjustment due to rate transitions on R-SCH inaccordance with an embodiment.

FIG. 3 shows scheduling delay timing in accordance with an embodiment;

FIG. 4 shows parameters associated in mobile station scheduling on areverse link;

FIG. 5 is a flowchart of a scheduling process in accordance with anembodiment;

FIG. 6 is a block diagram of a base station in accordance with anembodiment; and

FIG. 7 is a block diagram of a mobile station in accordance with anembodiment.

DETAILED DESCRIPTION

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

A wireless communication system may comprise multiple mobile stationsand multiple base stations. FIG. 1 exemplifies an embodiment of awireless communication system with three mobile stations 10A, 10B and10C and two base stations 12. In FIG. 1, the three mobile stations areshown as a mobile telephone unit installed in a car 10A, a portablecomputer remote 10B, and a fixed location unit 10C such as might befound in a wireless local loop or meter reading system. Mobile stationsmay be any type of communication unit such as, for example, hand-heldpersonal communication system units, portable data units such as apersonal data assistant, or fixed location data units such as meterreading equipment. FIG. 1 shows a forward link 14 from the base station12 to the mobile stations 10 and a reverse link 16 from the mobilestations 10 to the base stations 12.

As a mobile station moves through the physical environment, the numberof signal paths and the strength of the signals on these paths varyconstantly, both as received at the mobile station and as received atthe base station. Therefore, a receiver in an embodiment uses a specialprocessing element called a searcher element, that continually scans thechannel in the time domain to determine the existence, time offset, andthe signal strength of signals in the multiple path environment. Asearcher element is also called a search engine. The output of thesearcher element provides the information for ensuring that demodulationelements are tracking the most advantageous paths.

A method and system for assigning demodulation elements to a set ofavailable signals for both mobile stations and base stations isdisclosed in U.S. Pat. No. 5,490,165 entitled “DEMODULATION ELEMENTASSIGNMENT IN A SYSTEM CAPABLE OF RECEIVING MULTIPLE SIGNALS,” issuedFeb. 6, 1996, and assigned to the Assignee of the present.

When multiple mobiles transmit simultaneously, the radio transmissionfrom one mobile acts as interference to the other mobile's radiotransmission, thereby limiting throughput achievable on the reverse link(also called the uplink). For efficient capacity utilization on thereverse link, centralized scheduling at the base station has beenrecommended in U.S. Pat. No. 5,914,950 entitled “METHOD AND APPARATUSFOR REVERSE LINK RATE SCHEDULING,” issued Jun. 22, 1999, and U.S. Pat.No. 5,923,650 entitled “METHOD AND APPARATUS FOR REVERSE LINK RATESCHEDULING,” issued Jul. 13, 1999, both of which are assigned to theAssignee of the present.

In an exemplary embodiment, multi-level scheduling is performed. In anembodiment, multi-level scheduling comprises base station levelscheduling, selector level scheduling, and/or network level scheduling.

In an embodiment, a detailed design of a flexible scheduling algorithmis based on fundamental theoretical principles that limit reverse-linksystem capacity, while using existing network parameters available ormeasured by a base station.

In an embodiment, base-station estimation of each mobile's capacitycontribution is based on measured signal-to-noise ratio (Snr) or pilotenergy over noise plus interference ratio (Ecp/(Io+No)), collectivelycalled (Ecp/Nt), given the current rate of transmission. Measurement ofpilot Ecp/Nt from all fingers in multi-path scenario is disclosed inU.S. application Ser. No. 10/011,519 entitled “METHOD AND APPARATUS FORDETERMINING REVERSE LINK LOAD LEVEL FOR REVERSE LINK DATA RATESCHEDULING IN A CDMA COMMUNICATION SYSTEM,” filed Nov. 5, 2001, andassigned to the assignee of the present invention.

From the measurement of pilot Ecp/Nt at current rates on differentchannels, capacity contribution of a mobile is estimated at new rates onthese channels.

In an embodiment, mobile requests for rate allocation are prioritized. Alist of all mobiles that a scheduler is responsible for scheduling ismaintained depending on which level the scheduling is performed. In anembodiment, there is one list for all the mobiles. Alternatively, thereare two lists for all mobiles. If the scheduler is responsible forscheduling all the base stations a mobile has in its Active Set, thenthe mobile belongs to a First List. A separate Second List may bemaintained for those mobiles that have a base station in the Active Setthat the scheduler is not responsible for scheduling. Prioritization ofmobile rate requests is based on various reported, measured or knownparameters that maximize system throughput, while allowing for mobilefairness as well as their importance status.

In an embodiment, Greedy Filling is used. In Greedy Filling, a highestpriority mobile obtains the available sector capacity. A highest ratethat can be allocated to the mobile is determined as the highest ratethat the mobile can transmit at. In an embodiment, the highest rates aredetermined based on measured SNR. In an embodiment, the highest ratesare determined based on Ecp/Nt. In an embodiment, the highest rates aredetermined based also on limiting parameters. In an embodiment, thehighest rate is determined by a mobile's buffer estimate. The choice ofa high rate decreases the transmission delays and decreases interferencethat the transmitting mobile observes. Remaining sector capacity can beallocated to the next lower priority mobile. This methodology helps inmaximizing the gains due to interference reduction while maximizing thecapacity utilization.

By the choice of different prioritization functions, the Greedy Fillingalgorithm can be tuned to the conventional round-robin, proportionallyfair or most unfair scheduling based on a specified cost metric. Underthe class of scheduling considered, the above method helps aid maximumcapacity utilization.

The mobile station initiates a call by transmitting a request message tothe base station. Once the mobile receives a channel assignment messagefrom base station, it can use logical dedicated channel for furthercommunication with the base-station. In a scheduled system, when themobile station has data to transmit, it can initiate the high-speed datatransmission on the reverse link by transmitting a request message onthe reverse link.

Rate request and rate allocation structure currently specified in IS2000 Release C is considered. However, it would be apparent to thoseskilled in the art that the scope of the design is not limited to IS2000. It would be apparent to those skilled in the art, that embodimentsmay be implemented in any multiple access system with a centralizedscheduler for rate allocation.

Mobile Station Procedures

In an embodiment, mobile stations (MS) at least support the simultaneousoperation of the following channels:

1. Reverse Fundamental Channel (R-FCH)

2. Reverse Supplemental Channel (R-SCH)

Reverse Fundamental Channel (R-FCH): When a voice-only MS has an activevoice-call, it is carried on the R-FCH. For data-only MS, R-FCH carriessignaling and data. Exemplary R-FCH channel frame size, coding,modulation and interleaving are specified in TIA/EIA-IS-2000.2, “MobileStation-Base Station Compatibility Standard for Dual-Mode WidebandSpread Spectrum Cellular System,” June, 2002.

In an exemplary embodiment, R-FCH at a null rate is used for outer-looppower control (PC), when an MS is not transmitting voice, data orsignaling on R-FCH. Null rate means a lowest rate. R-FCH at a lowestrate may be used to maintain outer-loop power control even when there isno transmission on R-SCH.

Reverse Supplemental Channel (R-SCH): The MS supports one R-SCH forpacket data transmissions in accordance with an embodiment. In anexemplary embodiment, the R-SCH uses rates specified by radioconfiguration (RC3) in TIA/EIA-IS-2000.2.

In an embodiment where only single data channel (R-SCH) is supported,the signaling and power control can be done on a control channel.Alternatively, signaling can be carried over R-SCH and outer-loop PC canbe carried on R-SCH whenever it is present.

In an embodiment, the following procedures are followed by mobilestations:

-   -   Multiple Channel Adjustment Gain    -   Discontinuous Transmission and Variable Supplemental Adjustment        Gain    -   Overhead transmission of R-CQICH and other control channels    -   Closed-loop Power Control (PC) command    -   Rate request using a Supplemental Channel Request Mini Message        (SCRMM) on a 5-ms R-FCH or a Supplemental Channel Request        Message (SCRM) on a 20-ms R-FCH

Multiple Channel Adjustment Gain: When the R-FCH and the R-SCH aresimultaneously active, multiple channel gain table adjustment asspecified in TIA/EIA-IS-2000.2 is performed to maintain correcttransmission power of the R-FCH. The traffic-to-pilot (T/P) ratios forall channel rate are also specified in the Nominal Attribute Gain tablein appendix A as Nominal Attribute Gain values. Traffic-to-pilot ratiomeans the ratio of traffic channel power to pilot channel power.

Discontinuous Transmission and Variable Supplemental Adjustment Gain:The MS may be assigned an R-SCH rate by a scheduler during eachscheduling period. When the MS is not assigned an R-SCH rate, it willnot transmit anything on the R-SCH. If the MS is assigned to transmit onthe R-SCH, but it does not have any data or sufficient power to transmitat the assigned rate, it disables transmission (DTX) on the R-SCH. Ifthe system allows it, the MS may be transmitting on the R-SCH at a ratelower than the assigned one autonomously. In an embodiment, thisvariable-rate R-SCH operation is accompanied by the variable rate SCHgain adjustment as specified in TIA/EIA-IS-2000.2. R-FCH T/P is adjustedassuming the received pilot SNR is high enough to support the assignedrate on R-SCH.

Overhead transmission of R-CQICH and other control channels: A data-onlyMS transmits extra power on CQICH and/or other control channels at aCQICH-to-pilot (or control-to-pilot) (C/P) ratio with multi-channel gainadjustment performed to maintain correct transmission power of theR-CQICH (or control channels). (C/P) value may be different for MS insoft-handoff from those not in soft handoff. (C/P) represent the ratioof total power used by the control channels to the pilot power withoutmultichannel gain adjustment.

Closed-loop Power Control (PC) command: In an embodiment, an MS receivesone PC command per power control group (PCG) at a rate of 800 Hz fromall base stations (BSs) in the MS's Active Set. A PCG is a 1.25 msinterval on the Reverse Traffic Channel and the Reverse Pilot Channel.Pilot power is updated by +−1 dB based on an “Or-of-Downs” rule, aftercombining of the PC commands from co-located BSs (sectors in a givencell).

Rate request is done with one of two methods. In a first method, raterequest is performed using a Supplemental Channel Request Mini Message(SCRMM) on a 5-ms R-FCH as specified in TIA/EIA-IS-2000.5.

Supplemental Channel Request Mini Message (SCRMM) on a 5-ms R-FCH: In anembodiment, each SCRMM transmission is 24 bits (or 48 bits with thephysical layer frame overhead in each 5-ms FCH frame at 9.6 kbps).

The MS sends the SCRMM in any periodic interval of 5 ms. If a 5-ms SCRMMneeds to be transmitted, the MS interrupts its transmission of thecurrent 20-ms R-FCH frame, and instead sends a 5-ms frame on the R-FCH.After the 5-ms frame is sent, any remaining time in the 20-ms period onthe R-FCH is not transmitted. The discontinued transmission of the 20-msR-FCH is re-established at the start of next 20-ms frame.

In a second method, rate request is performed using a SupplementalChannel Request Message (SCRM) on a 20-ms R-FCH.

Depending on different embodiments, different information can be sent ona request message. In IS2000, Supplemental Channel Request Mini Message(SCRMM) or a Supplemental Channel Request Message (SCRM) is sent on thereverse-link for rate request.

In an embodiment, the following information shall be reported by the MSto the BS on each SCRM/SCRMM transmission:

-   -   Maximum Requested Rate    -   Queue Information

Maximum Requested Rate: It can be the maximum data rate an MS is capableof transmitting at the current channel conditions leaving headroom forfast channel variations. An MS may determine its maximum rate using thefollowing equation:

${{{R_{\max}({power})} = {\underset{R}{\arg\mspace{11mu}\max}\begin{Bmatrix}{R:{{{Pref}(R)}*{{NormAvPiTx}\left( {PCG}_{i} \right)}*}} \\\left( {1 + \left( {T/P} \right)_{R} + {\left( {\left( {T/P} \right)_{9.6k} + {C/P}} \right)\left( \frac{{Pref}\left( {9.6k} \right)}{{Pref}(R)} \right)}} \right) \\{\leq {{{Tx}\left( \max \right)}/{Headroom\_ Req}}}\end{Bmatrix}}}{{{NormAvPiTx}\left( {PCG}_{i} \right)} = {{\alpha_{Headroom}\frac{{TxPiPwr}\left( {PCG}_{i} \right)}{{Pref}({Rassigned})}} + {\left( {1 - \alpha_{Headroom}} \right) \times {{NormAvPiTx}\left( {PCG}_{i - 1} \right)}}}}},$where Pref(R) is the “Pilot Reference Level” value specified in theAttribute Gain Table in TIA/EIA-IS-2000.2, TxPiPwr(PCG_(i)) is theactual transmit pilot power after power constraints on the MS side areapplied in case of power outage, and NormAvPiTx(PCG_(i)) is thenormalized average transmit pilot power. An MS may be more conservativeor aggressive in its choice of headroom and determination of maximumrequested rate depending on what is permitted by the BS.

In an embodiment, the MS receives grant information by one of the twofollowing methods:

Method a: Enhanced supplemental channel assignment mini message (ESCAMM)from BS on 5-ms forward dedicated control channel (F-DCCH) with rateassignment for specified scheduling duration.

Method b: Enhanced supplemental channel assignment message (ESCAM) fromBS on forward physical data channel (F-PDCH) with rate assignment forspecified scheduling duration.

The assignment delays depend on the backhaul and transmission delays andare different depending on which method is used for rate grant. Duringthe scheduled duration, the following procedures are performed:

-   -   In an embodiment where R-FCH is used to transmit autonomous data        and for outer-loop PC, the MS transmits data at an autonomous        rate of 9600 bps if it has some data in its buffer. Otherwise,        the MS sends a null R-FCH frame at a rate of 1500 bps.    -   The MS transmits at the assigned R-SCH rate in a given 20-ms        period if the MS has more data than can be carried on the R-FCH        and if the MS has decided that it would have sufficient power to        transmit at the assigned rate (keeping headroom for channel        variations). Otherwise, there is no transmission on the R-SCH        during the frame or the MS transmits at a lower rate which        satisfies the power constraint. The MS decides that it has        sufficient power to transmit on the R-SCH at the assigned rate R        in a given 20-ms period Encode_Delay before the beginning of        that 20-ms period if the following equation is satisfied:

${{{Pref}(R)}*{{{NormAvPiTx}\left( {PCG}_{i} \right)}\left\lbrack {1 + \left( {T/P} \right)_{R} + {\left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)\left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}(R)} \right)}} \right\rbrack}} < \frac{{Tx}\left( \max \right)}{Headroom\_ Tx}$where Pref(R) is the “Pilot Reference Level” value specified in theAttribute Gain Table in TIA/EIA-IS-2000.2, NormAvPiTx(PCG_(i)) is thenormalized average transmit pilot power, (T/P)_(R) is the traffic topilot ratio that corresponds to rate R and for all channel rates isspecified in the Nominal Attribute Gain table in appendix A as NominalAttribute Gain values, (T/P)_(RFCH) is the traffic to pilot ratio onFCH, (C/P) is the ratio of total power used by the control channels tothe pilot power without multichannel gain adjustment, T_(x)(max) is themaximum MS transmit power, and Headroom_Tx is the headroom the MS keepsto allow for channel variation.

The DTX determination is done once every frame, Encode_Delay PCGs beforethe R-SCH transmission. If the MS disables transmission on the R-SCH, ittransmits at the following power:

${{TxPwr}\left( {PCG}_{i} \right)} = {{{PiTxPwr}\left( {PCG}_{i} \right)}\left\lbrack {1 + {\left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)\left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}(R)} \right)}} \right\rbrack}$

An MS encodes the transmission frame Encode_Delay before the actualtransmission.

Base Station Procedures

In an embodiment, the BS performs the following essential functions:

-   -   Decoding of R-FCH/R-SCH    -   Power control        Decoding of R-FCH/R-SCH

When there are multiple traffic channels transmitted by the MSsimultaneously, each of the traffic channels is decoded aftercorrelating with the corresponding Walsh sequence.

Power-Control

Power control in a CDMA system is essential to maintain the desiredquality of service (QoS). In IS-2000, the RL pilot channel (R-PICH) ofeach MS is closed-loop power controlled to a desired threshold. At theBS, this threshold, called power control set point, is compared againstthe received Ecp/Nt to generate power control command (closed-loop PC),where Ecp is the pilot channel energy per chip. To achieve the desiredQoS on the traffic channel, the threshold at the BS is changed witherasures on the traffic channel, and has to be adjusted when the datarate changes.

Set point corrections occur due to:

-   -   Outer-loop power control    -   Rate Transitions

Outer-loop power control: If the R-FCH is present, the power control setpoint is corrected based on erasures of the R-FCH. If R-FCH is notpresent, the outer-loop PC is corrected based on erasures of somecontrol channel or R-SCH when the MS is transmitting data.

Rate Transitions: Different data rates on the R-SCH require differentoptimal set point of the reverse pilot channel. When data rate changeson the R-SCH, the BS changes the MS's received Ecp/Nt by the PilotReference Levels (Pref(R)) difference between the current and the nextR-SCH data rate. In an embodiment, the Pilot Reference Level for a givendata rate R, Pref(R), is specified in the Nominal Attribute Gain Tablein C.S0002-C. Since the closed-loop power control brings the receivedpilot Ecp/Nt to the set point, the BS adjusts the outer loop set pointaccording to the next assigned R-SCH data rate:Δ=Pref(Rnew)−Pref(Rold)

Set point adjustment is done ┌Δ┐ PCGs in advance of the new R-SCH datarate if R_(new)>R_(old). Otherwise, this adjustment occurs at the R-SCHframe boundary. The pilot power thus ramps up or down to the correctlevel approximately in 1 dB step sizes of the closed loop as shown inFIG. 2.

FIG. 2 shows set point adjustment due to rate transitions on R-SCH inaccordance with an embodiment. The vertical axis of FIG. 2 shows asetpoint of a base station controller (BSC) 202, a base transceiversubsystem (BTS) receiver pilot power 204, and the mobile station rate206. The MS rate is initially at R₀ 208. When the R-SCH data rateincreases, i.e., R1>R0 210, then the setpoint is adjusted according toP_(ref)(R₁)−P_(ref)(R₀) 212. When the R-SCH data rate decreases, i.e.,R2<R1 214, then the setpoint is adjusted according toP_(ref)(R₂)−P_(ref)(R₁) 216.

Scheduler Procedures

A scheduler may be collocated with the BSC, or BTS or at some element inthe network layer. A Scheduler may be multilevel with each partresponsible for scheduling those MSs that share the lower layerresources. For example, the MS not in soft-handoff (SHO) may bescheduled by BTS while the MS in SHO may be scheduled by part of thescheduler collocated with BSC. The reverse-link capacity is distributedbetween BTS and BSC for the purpose of scheduling.

In an embodiment, the following assumptions are used for the schedulerand various parameters associated with scheduling in accordance with anembodiment:

1. Centralized Scheduling: The scheduler is co-located with the BSC, andis responsible for simultaneous scheduling of MSs across multiple cells.

2. Synchronous Scheduling: All R-SCH data rate transmissions are timealigned. All data rate assignments are for the duration of onescheduling period, which is time aligned for all the MSs in the system.The scheduling duration period is denoted SCH_PRD.

3. Voice and Autonomous R-SCH transmissions: Before allocating capacityto transmissions on R-SCH through rate assignments, the scheduler looksat the pending rate requests from the MSs and discounts for voice andautonomous transmissions in a given cell.

4. Rate Request Delay: The uplink request delay associated with raterequesting via SCRM/SCRMM is denoted as D_RL(request). It is the delayfrom the time the request is sent to when it is available to thescheduler. D_RL(request) includes delay segments for over-the-airtransmission of the request, decode time of the request at the cells,and backhaul delay from the cells to the BSC, and is modeled as auniformly distributed random variable.

5. Rate Assignment Delay: The downlink assignment delay associated withrate assignment via ESCAM/ESCAMM is denoted as D_FL(assign). It is thetime between the moment the rate decision is made and the time the MSreceiving the resultant assignment. D_FL(assign) includes backhaul delayfrom the scheduler to the cells, over-the-air transmission time of theassignment (based on method chosen), and its decode time at the MS.

6. Available Ecp/Nt Measurement: The Ecp/Nt measurement used in thescheduler shall be the latest available to it at the last frameboundary. The measured Ecp/Nt is reported to the scheduler by the BTSreceiver periodically and so it is delayed for a BSC receiver.

FIG. 3 shows scheduling delay timing in accordance with an embodiment.The numbers shown are an example of typical numbers that may be used bya BSC located scheduler though the actual numbers are dependent onbackhaul delays and loading scenario of the deployed system.

The horizontal axis shows an SCH frame boundary 250, a last SCH frameboundary before a point A 252, a point A 254, a scheduling time 256, andan action time 258. An Ec/Nt measurement window 260 is shown starting atthe SCH frame boundary 250 and ending at the last SCH frame boundarybefore point A 252. A time to last frame boundary 262 is shown from thelast SCH frame boundary before point A 252 to point A 254. A time to getinformation from the BTS to the BSC (6 PCGs) 264 is shown starting atpoint A 254 and ending at the scheduling time 256. ActionTimeDelay (25PCGs for Method a, 62 PCGs for Method b) 266 is shown to start at thescheduling time 256 and ending at the action time 258.

Scheduling, Rate Assignment and Transmission Timeline

Given the assumed synchronous scheduling, most events related torequest, grant and transmission are periodic with period SCH_PRD.

FIG. 4 illustrates the timing diagram of a rate request, scheduling andrate allocation in accordance with an embodiment. The vertical axes showthe time lines for the BSC (scheduler) 402 and the mobile 404. The MScreates an SCRMM 406 and sends a rate request to the BSC (scheduler)408. The rate request is included in the SCRMM, which is sent on R-FCH.The uplink request delay associated with rate requesting via SCRM/SCRMMis denoted as D_RL(request) 410. A scheduling decision 412 is made onceevery scheduling period 414. After the scheduling decision 412, anESCAM/ESCAMM 416 is sent on a forward channel from the BSC to the MSindicating a rate assignment 418. D_FL 420 is the downlink assignmentdelay associated with rate assignment via ESCAM/ESCAMM. Turnaround time422 is the time it takes to turnaround a rate request. It is the timefrom the rate request to rate assignment.

The following characterizes the timeline:

-   -   Scheduling Timing    -   Scheduled Rate Transmissions    -   MS R-SCH Rate Requests

Scheduling Timing: The scheduler operates once every scheduling period.If the first scheduling decision is performed at t_(i), then thescheduler operates at t_(i), t_(i)+SCH_PRD, t_(i)+2SCH_PRD . . . .

Scheduled Rate Transmissions: Given that the MSs have to be notified ofthe scheduling decisions with sufficient lead-time, a schedulingdecision has to be reached at Action Time of the ESCAM/ESCAMM messageminus a fixed delay, ActionTimeDelay. Typical values of ActionTimeDelayfor Methods a and b are given in Table 1.

MS R-SCH Rate Requests: R-SCH rate requests are triggered as describedbelow:

Before the beginning of each SCRM/SCRMM frame encode boundary, the MSchecks if either of the following three conditions are satisfied:

1. New data arrives and data in the MS's buffer exceeds a certain bufferdepth (BUF_DEPTH), and the MS has sufficient power to transmit at anon-zero rate; OR

2. If the last SCRM/SCRMM was sent at time τ_(i), and the current timeis greater than or equal to τ_(i)+SCH_PRD and if the MS has data in itsbuffer that exceeds the BUF_DEPTH, and the MS has sufficient power totransmit at a non-zero rate; OR

3. If the last SCRM/SCRMM was sent at time τ_(i), and the current timeis greater than or equal to τ_(i)+SCH_PRD, and if the current assignedrate at the MS side based on received ESCAMM/ESCAM is non-zero(irrespective of the fact that the MS may not have data or power torequest a non-zero rate). “Current assigned rate” is the assigned rateapplicable for the current rate transmission. If no ESCAM is receivedfor the current scheduled duration, then the assigned rate is considered0. The rate assigned in the ESCAM/ESCAMM message with Action Time atsome later time takes effect after the Action Time.

If either of the above three conditions are satisfied, the MS sends aSCRMM/SCRM rate request.

In an embodiment, an SCRM/SCRMM request made at τ_(i) is made availableto the scheduler after a random delay at τ_(i)+D_RL(request). In anotherembodiment, different combinations of change in MS data buffer, changein MS maximum supportable rate and MS last request time out may be usedto determine the time when a rate request is sent.

Scheduler Description and Procedures

In an embodiment, there is one centralized scheduler element for a largenumber of cells. The scheduler maintains a list of all MSs in the systemand BSs in each MS's Active Set. Associated with each MS, the schedulerstores an estimate of an MS's queue size ({circumflex over (Q)}) andmaximum scheduled rate (Rmax(s)).

The queue size estimate {circumflex over (Q)} is updated after any ofthe following events happen:

1. An SCRMM/SCRM is received: SCRMM/SCRM is received after a delay ofD_RL(request). {circumflex over (Q)} is updated to:{circumflex over (Q)}=Queue Size reported in SCRMM

If the SCRMM/SCRM is lost, the scheduler uses the previous (and thelatest) information it has.

2. After each R-FCH and R-SCH frame decoding:{circumflex over (Q)}={circumflex over(Q)}−Data_(tx)(FCH)+Data_(tx)(SCH)

where Data_(tx)(FCH) and Data, Data_(tx)(SCH) is the data transmitted inthe last R-FCH and R-SCH frame, respectively (if the frame is decodedcorrectly) after discounting the physical layer overhead and RLP layeroverhead.

3. At the scheduling instant t_(i), scheduler estimates the maximumscheduled rate for the MS in accordance with an embodiment. The buffersize estimation is done as:{circumflex over (Q)}(f)={circumflex over (Q)}−(R_(assigned)+9600)×┌ActionTimeDelay/20┐·20ms+((PL _(—) FCH _(—) OHD+SCH_(Assigned) *PL _(—) SCH _(—) OHD)×(┌ActionTimeDelay/20┐)

The maximum scheduled rate is obtained as the minimum of the maximumpower constrained rate and maximum buffer size constrained rate. Maximumpower constrained rate is the maximum rate that can be achieved with MSavailable power, and maximum buffer size constrained rate is the maximumrate such that the transmitted data is smaller or equal to the estimatedbuffer size.

${R_{\max}(s)} = {\min\begin{Bmatrix}{{R_{\max}({power})},} \\{\underset{\underset{R \leq {307.2\mspace{11mu}{kbps}}}{R}}{\arg\;\max}\left\{ R \middle| {{\hat{Q}(f)} \geq \left( {{\left( {R + 9600} \right) \times 20\mspace{11mu}{ms}} - {{PL\_ FCH}{\_ OHD}}} \right.} \right.} \\\left. \left. {\left. {{- {PL\_ SCH}}{\_ OHD}} \right) \times {({SCH\_ PRD})/20}\mspace{11mu}{ms}} \right) \right\}\end{Bmatrix}}$where SCH_(Assigned) is an indicator function for the current schedulingperiod,

${SCH}_{Assigned} = \left\{ \begin{matrix}1 & {{{if}\mspace{14mu} R_{assigned}} > 0} \\0 & {{{if}\mspace{14mu} R_{assigned}} = 0}\end{matrix} \right.$

R_(assigned) is the rate assigned on the R-SCH during the currentscheduling period and MS is supposed to transmit on the R-SCH until theActionTime of the next assignment. PL_FCH_OHD is physical layerfundamental channel overhead. PL_SCH_OHD is physical layer supplementalchannel overhead.

R_(max)(power) is the maximum rate that the MS can support given itspower limit. If the maximum requested rate by the MS is determinedaccording to an embodiment described herein, R_(max)(power) is themaximum rate reported in the last received SCRM/SCRMM message. If themaximum rate is determined according to a different embodiment, thescheduler can estimate R_(max)(power) from the reported information andMS capability to transmit at the assigned rate. For example, in anotherembodiment, the scheduler can estimate R_(max)(power) according to theequation below:

${R_{\max}({power})} = \begin{Bmatrix}{{\min\left\{ {{R({reported})},{R_{assigned} + 1}} \right\}};{{{if}\mspace{14mu} R_{tx}} = R_{assigned}}} \\{{\min\left\{ {{R({reported})},{R_{assigned} - 1}} \right\}};{{{if}\mspace{14mu} R_{tx}} < R_{assigned}}}\end{Bmatrix}$

R_(assigned) is the rate assigned during current scheduling period andR_(tx) is the rate transmitted on R-SCH during current schedulingperiod. R_(assigned)+1 is rate one higher than what is currentlyassigned to the MS and R_(assigned)−1 is a rate one lower than what iscurrently assigned to the MS. R(reported) is the maximum rate reportedby the MS in rate request message like SCRM/SCRMM. The above method maybe used when R(reported) by the MS is not related to the maximum ratethat MS is capable of transmitting at its current power constraints.

Arg max provides the maximum supportable rate by the scheduler.

Capacity Computation

The sector capacity at the jth sector is estimated from the measuredMSs' Sinrs. The Sinr is the average pilot-weighted combined Sinr perantenna. In an embodiment, the combining per power-control group (PCG)is pilot-weighted combining over multiple fingers and different antennasof the sector of interest. In an embodiment, the combining perpower-control group (PCG) is maximal ratio combining over multiplefingers and different antennas. The combining is not over differentsectors in the case of a softer-handoff MS. The averaging can be overthe duration of a frame or it can be a filtered average over a couple ofPCGs.

The following formula is used for estimating Load contribution to asector antenna:

${Load}_{j} = {\sum\limits_{j \in {{ActiveSet}{(i)}}}\frac{{Sinr}_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {R_{i},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}$where Sinr_(j)(R_(i),E[R_(FCH)]) is the estimated Sinr if the MS isassigned a rate R_(i) on R-SCH and E[R_(FCH)] is the expected rate oftransmission on the R-FCH.

Let the measured pilot Sinr (frame average or filtered average pilotSinr averaged over two antennas) be (E_(cp)/N_(t))_(j), while it isassigned a rate of Rassign (SCH) on the R-SCH. Then,

${{Sinr}_{j}\left( {R_{i},R_{FCH}} \right)} = {\frac{{Pref}\left( R_{i} \right)}{{Pref}\left( {R_{assign}({SCH})} \right)}{\left( {E_{cp}/N_{t\;}} \right)_{j}\left\lbrack {1 + \left( {T/P} \right)_{R_{i}} + {\left( {\left( {T/P} \right)_{R_{FCH}} + \left( {C/P} \right)} \right)\left( \frac{{Pref}\left( R_{FCH} \right)}{{Pref}\left( R_{i} \right)} \right)}} \right\rbrack}}$

C/P can be an average (CQICH/Pilot) or a (Control-to-pilot) ratio.

For voice-only MSs, the following equation is used to estimate theaverage received Sinr:

${{Sinr}_{j}\left( {0,{E\left\lbrack {R_{FCH}(\upsilon)} \right\rbrack}} \right)} = {\frac{\left( {E_{cp}/N_{t}} \right)_{j}}{{Pref}\left( {R_{assisgn}({SCH})} \right)} \times \left\lbrack {1 + {\begin{pmatrix}{{\left( {T/P} \right)_{9.6k}{P\left( {9.6k} \right)}} +} \\{{\left( {T/P} \right)_{4.8k}{P\left( {4.8k} \right)}} +} \\{{\left( {T/P} \right)_{2.7k}{P\left( {2.7k} \right)}} +} \\\left( {{\left( {T/P} \right)_{1.5k}{P\left( {1.5k} \right)}} +} \right. \\\left( {C/P} \right)\end{pmatrix}{{Pref}\left( {R_{FCH}^{\max} = {9.6k}} \right)}}} \right\rbrack}$where P(R) is the probability of voice codec transmitting at that rate.In another embodiment where a different voice codec with different rateselections are used, the same equation is used with different rates toestimate the expected Sinr due to voice transmission on R-FCH.

In a more generic formulation, with data-voice mobiles and no datatransmission on R-FCH, the voice-activity factor (υ) could be used toestimate the average received Sinr as follows:

${{Sinr}_{j}\left( {R_{i},{E\left\lbrack {R_{FCH}(\upsilon)} \right\rbrack}} \right)} = {\frac{{{Pref}\left( R_{i} \right)}\left( {E_{cp}/N_{t}} \right)_{j}}{{Pref}\left( {R_{assign}({SCH})} \right)}\left\lbrack {1 + \left( {T/P} \right)_{R_{i}} + {\left( {\upsilon - 1 + {\upsilon\left( {T/P} \right)}_{R_{FCH}^{\max}}} \right)\left( \frac{{Pref}\left( R_{FCH}^{\max} \right)}{{Pref}\left( R_{i} \right)} \right)}} \right\rbrack}$

If the interference from neighboring sectors and average thermal noisecan be measured, a more direct measure of the capacity of reverse-linkcalled rise-over-thermal (ROT) can be obtained. Let the other-cellinterference measured during previous transmission be denoted as I_(oc),thermal noise be N_(o), then the estimated ROT during the nexttransmission can be estimated as

${ROT}_{j} = {\frac{1}{\left( {1 - {Load}_{j}} \right)}{\left( {1 + {I_{oc}/N_{o}}} \right).}}$

If the scheduler is multi-level scheduler, with different levels of thescheduler elements scheduling different MSs, the sector capacity needsto be distributed across different scheduling elements. In anembodiment, where the scheduler has two scheduling elements, one at aBTS and the other at a BSC, let the estimated assigned Load at BSC beLoad_(j)(BSC) and the estimated assigned load at BTS be Load_(j)(BTS).Then,Load_(j)(BSC)+Load_(j)(BTS)<=1−(1+I _(oc) /N _(o))/ROT(max).

Since the timing delay in scheduling at BSC is greater than BTS,estimated assigned load at BSC Load_(j)(BSC) can be known at BTS priorto scheduling at BTS. BTS scheduler prior to scheduling then hasfollowing constraint on the assigned load:Load_(j)(BTS)<=1−(1+I _(oc) /N _(o))/ROT(max)−Load_(j)(BSC)Scheduling Algorithm

The scheduling algorithm has the following characteristics:

a) scheduling least number of MS for increasing TDM gains,

b) CDM few users for maximum capacity utilization, and

c) prioritization of MS rate requests.

Prioritization of mobiles can be based on one or more of the variedreported or measured quantities. A priority function that increasessystem throughput can have one or many of the following characteristics:

The higher the measured pilot Ecp/Nt (normalized), the lower is themobile's priority. Instead of using a measured Ecp/Nt, a pilot Ecp/Ntset-point that the base-station maintains for power control outer-loopcould be used. A lower Ecp/Nt (measured or set-point) implies a betterinstantaneous channel and hence increased throughput if channelvariations are small.

For a mobile in SHO, pilot Ecp/Nt (measured or Set-point) can beweighted by an SHOfactor to reduce the other-cell interference. Forexample, if average received pilot powers at all SHO legs is available,

${\sum\limits_{k = 1}^{M}{{{P_{i}^{rx}(k)}/{P_{i}^{rx}(j)}}\mspace{14mu}{can}\mspace{14mu}{serve}\mspace{14mu}{as}\mspace{14mu}{an}\mspace{14mu}{SHO}{\mspace{11mu}\;}{factor}}},$where P_(i) ^(rx) (k) is the average received pilot power of the i^(th)mobile by the k^(th) base station in its Active Set, P_(i) ^(rx) (j) isthe average received pilot power of the i^(th) mobile by the strongest,j^(th) base station in its Active Set, and M is the number of basestations in the mobile's Active Set (set of base stations in softhandoff with the mobile)

Higher the measured or estimated propagation loss, lesser is thepriority. Propagation Loss can be calculated from the measured receivedpilot power if the mobile periodically reports transmitted pilot powerin the request message like SCRM. Or otherwise, it can estimate whichmobile sees better propagation loss based on the reported strength ofthe FL Ecp/Nt

Velocity based priority function: If the base-station estimated velocityof a moving mobile using some velocity estimation algorithm, thenstationary mobiles are given the highest priority, and middle velocitymobiles are given the least priority.

Priority function based on above measured or reported parameters is anunfair priority function aimed at increasing the reverse-link systemthroughput. In addition, priority can be increased or decreased by acost metric that is decided by what grade of service a user isregistered for. In addition to the above, a certain degree of fairnesscould be provided by a Fairness factor. Two different kinds of Fairnessare described below:

Proportional Fairness (PF): PF is the ratio of maximum requested rate toaverage achieved transmission rate. Thus, PF=R_(i) ^(req)/R_(i)^(alloc), where R_(i) ^(req) is the requested rate and R_(i) ^(alloc) isthe average rate allocated by the scheduler.

Round Robin Fairness (RRF): Round robin scheduling tries to provideequal transmission opportunities to all the users. When a mobile entersthe system, RRF is initialized to some value, say 0. Each schedulingperiod the rate is not allocated to the mobile, RRF is incremented byone. Every time some rate (or the requested rate) is allocated to themobile, RRF is reset to the initial value 0. This emulates the processwhere mobiles scheduled in the last scheduling period are last in thequeue.

Fairness can be used together with Priority function to determine thepriority of the mobile in the Prioritization list. When Fairness is usedalone to prioritize mobiles, it provides proportional fair orround-robin scheduling that is throughput optimal for reverse-link aswell as allowing multiple transmissions for full capacity utilization.

An embodiment which uses different aspects of previously definedpriority functions and proportional fairness may have a priority of thei^(th) user determined as:

${w_{i} = {\frac{1}{{{Ecp}/{{Nt}_{i}({setpt})}}*{SHOfactor}} \cdot ({PF})^{\alpha}}},$

where the parameter α called Fairness factor can be used to trade-offfairness for system throughput. As α increases, fairness gets worse.Schedulers with higher α yield higher throughput.

Next we consider a particular embodiment where the scheduler wakes upevery scheduling period and makes rate allocation decisions based onpending rate requests. The scheduling algorithm looks like the onedescribed below.

Initialization: The MS rate requests are prioritized. Associated witheach MS is a priority count PRIORITY. PRIORITY of an MS is initializedto 0 in the beginning. When a new MS enters the system with sector j asthe primary sector, its PRIORITY is set equal to the min{PRIORITY_(i),∀i such that MS_(i) has sector j as the primary sector}

1. Let the Load constraint be Load_(j)≦max Load, such that therise-over-thermal overshoot above a certain threshold is limited. Forthe calibration purposes, max Load value of 0.45 will be used by thescheduler. The capacity consumed due to pilot transmissions andtransmissions on fundamental channels (due to voice or data) is computedand the available capacity is computed as

${{Cav}(j)} = {{\max\mspace{11mu}{Load}} - {\sum\limits_{j \in {ActiveSet}}\frac{{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}}$where max Load is the maximum Load for which rise-over-thermal outagecriteria specified is satisfied.

MS rate requests are prioritized in decreasing order of their PRIORITY.So MSs with highest PRIORITY are at the top of the queue. When multipleMSs with identical PRIORITY values are at the top of the queue, thescheduler makes a equally-likely random choice among these MSs.

2. Set k=1,

3. The data-only MS at the kth position in the queue is assigned therate R_(k) given by

$R_{k} = {\min\left\{ {{R_{\max}^{k}(s)},{\underset{R}{\arg\mspace{11mu}\max}\left\lbrack {\left. R \middle| {{{{Cav}(j)} - \frac{{Sinr},\left( {R,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {R,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}} + \frac{{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}} \geq 0} \right.;{\forall{j \in {{ActiveSet}(k)}}}} \right\rbrack}} \right\}}$

The available capacity is updated to:

${{{Car}(j)} = {{{Car}(j)} - \frac{{Sinr}_{j}\left( {R_{k},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {R_{k},{E\left\lbrack R_{FCH} \right\rbrack}} \right)}} + \frac{{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}{1 + {{Sinr}_{j}\left( {0,{E\left\lbrack R_{FCH} \right\rbrack}} \right)}}}};$∀j ∈ ActiveSet(k)

4. If R_(max) ^(k)(s)>0 and R_(k)=0, increment PRIORITY of the MS

Otherwise, do not change PRIORITY of the MS

5. k=k+1; if k<total number of MSs in the list, Go to Step 3, otherwise,stop.

TABLE 1 Baseline specific parameters Parameter Typical Values CommentsHeadroom_Req 5 dB Conservative rate request Keeps power headroom forlong-term channel variation Reduces DTX on R-SCH Headroom_Tx 2 dBReduces probability of power outage during the duration of R-SCHtransmission Average Tx Power Filter 1/16 Normalized Average transmitpilot Coefficient □_(Headroom) power is computed as filtered versionover several PCGs ActionTimeDelay 31.25 ms Based on the expected ESCAMMdelay, (Method a) including the 2 PCG MS encoding delay ActionTimeDelay77.5 ms Based on the expected ESCAM delay on (Method b) F-PDCH at theprimary sector Geometry of −5 dB. This includes the 2 PCG MS encodingdelay

It would be apparent to those skilled in the art that other values canbe used for the parameters in table 1. It would also be apparent tothose skilled in the art that more or less parameters may be used for aparticular implementation.

FIG. 5 is a flowchart of a scheduling process in an embodiment. In anembodiment, a mobile i and a mobile j send a request rate to a schedulerin step 300. Alternatively, a mobile i and a mobile j send a requestrate to a scheduler in step 310.

In step 300, the scheduler creates a list of mobiles (Mi) that it willschedule. Then, the scheduler creates a list of base stations (BTSs) thescheduler is responsible for scheduling. Also, the scheduler creates alist of mobiles that are not in the list of base stations the scheduleris responsible for scheduling and that are in soft handoff (SHO) withbase stations the scheduler is responsible for scheduling (U_(i)). Theflow of control goes to step 302.

The BTS supplies the scheduler with a reported DTX by a mobile. In step302, a check is made to determine whether a mobile, which is scheduled,reported a DTX, in which case resources can be reallocated from thescheduled mobile if a_(i) is less than the last schedule time minus 1plus a schedule period. ai is current time. t_(i) is the last scheduledtime. In step 302, the resources are reallocated before the scheduledtime. The rate of the scheduled mobile is reset and the availablecapacity is reallocated to other requesting mobiles. In step 306, acheck is made to determine whether the current time has reached ascheduled point. If the current time has not reached a scheduled point,then the flow of control goes to step 302. If the current time hasreached a scheduled point, then the flow of control goes to step 308.

In step 308, the scheduler is supplied by the BTSs with an estimate ofIoc and pilot Ec/Nt of {M_(i)}union{U_(i)}. The capacity of each Bi isinitialized given the loc estimates. For each Bi, subtracting from theavailable capacity, the voice users contribution to capacity given voiceactivity and autonomous transmission on R-FCH/R-DCCH. The measurementused for the amount subtracted is the pilot Ecp/Nt. Also for each Bi,subtracted from the available capacity is the expected contribution by{Ui}. Then, the flow of control goes to step 310.

In step 310, pilot Ec/Nt of {M_(i)} and set-point and Rx pilot power areprovided to the scheduler and are used by a prioritization function. Themobile rate requests are prioritized in a prioritization queue. In anembodiment, a prioritization function is used in which measured andreported information is used. In an embodiment, a prioritizationfunction provides for fairness. The flow of control goes to step 312.

In step 312, a maximum rate is assigned to a highest priority mobilesuch that a capacity constraint of all BSs in soft handoff is notviolated. The maximum rate is the maximum rate supported by the highestpriority mobile. The highest priority mobile is placed last in theprioritization queue. The available capacity is updated by subtractingthe mobile contribution to capacity at an assigned maximum rate. Theflow of control goes to step 314.

In step 314, a check is made to determine whether all the mobiles in the{Mi} list have been scanned. If all the mobiles in the {Mi} list havenot been scanned, then the flow of control goes to step 312. If all themobiles in the {Mi} list have been scanned, then the flow of controlgoes to step 302.

Those of skill in the art would understand that method steps could beinterchanged without departing from the scope of the invention. Those ofskill in the art would also understand that information and signalsmight be represented using any of a variety of different technologiesand techniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

FIG. 6 is a block diagram of a BS 12 in accordance with an embodiment.On the downlink, data for the downlink is received and processed (e.g.,formatted, encoded, and so on) by a transmit (TX) data processor 612.The processing for each channel is determined by the set of parametersassociated with that channel, and in an embodiment, may be performed asdescribed by standard documents. The processed data is then provided toa modulator (MOD) 614 and further processed (e.g., channelized,scrambled, and so on) to provide modulated data. A transmitter (TMTR)unit 616 then converts the modulated data into one or more analogsignals, which are further conditions (e.g., amplifies, filters, andfrequency upconverts) to provide a downlink signal. The downlink signalis routed through a duplexer (D) 622 and transmitted via an antenna 624to the designated MS(s).

FIG. 7 is a block diagram of an MS 106 in accordance with an embodiment.The downlink signal is received by an antenna 712, routed through aduplexer 714, and provided to a receiver (RCVR) unit 722. Receiver unit722 conditions (e.g., filters, amplifies, and frequency downconverts)the received signal and further digitizes the conditioned signal toprovide samples. A demodulator 724 then receives and processes (e.g.,descrambles, channelizes, and data demodulates) the samples to providesymbols. Demodulator 724 may implement a rake receiver that can processmultiple instances (or multipath components) of the received signal andprovide combined symbols. A receive (RX) data processor 726 then decodesthe symbols, checks the received packets, and provides the decodedpackets. The processing by demodulator 724 and RX data processor 726 iscomplementary to the processing by modulator 614 and TX data processor612, respectively.

On the uplink, data for the uplink, pilot data, and feedback informationare processed (e.g., formatted, encoded, and so on) by a transmit (TX)data processor 742, further processed (e.g., channelized, scrambled, andso on) by a modulator (MOD) 744, and conditioned (e.g., converted toanalog signals, amplified, filtered, and frequency upconverted) by atransmitter unit 746 to provide an uplink signal. The data processingfor the uplink is described by standard documents. The uplink signal isrouted through duplexer 714 and transmitted via antenna 712 to one ormore BSs 12.

Referring back to FIG. 6, at BS 12, the uplink signal is received byantenna 624, routed through duplexer 622, and provided to a receiverunit 628. Receiver unit 628 conditions (e.g., frequency downconverts,filters, and amplifies) the received signal and further digitizes theconditioned signal to provide a stream of samples.

In the embodiment shown in FIG. 6, BS 12 includes a number of channelprocessors 630 a through 630 n. Each channel processor 630 may beassigned to process the sample steam for one MS to recover the data andfeedback information transmitted on the uplink by the assigned MS. Eachchannel processor 630 includes a (1) demodulator 632 that processes(e.g., descrambles, channelizes, and so on) the samples to providesymbols, and (2) a RX data processor 634 that further processes thesymbols to provide the decoded data for the assigned MS.

Controllers 640 and 730 control the processing at the BS and the MS,respectively. Each controller may also be designed to implement all or aportion of the scheduling process. Program codes and data required bycontrollers 640 and 730 may be stored in memory units 642 and 732,respectively.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, a computer-readable medium or any other form of storage mediumknown in the art. An exemplary storage medium is coupled to theprocessor such the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor. The processor and the storagemedium may reside in an ASIC. The ASIC may reside in a user terminal. Inthe alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

APPENDIX A Reverse Link Nominal Attribute Gain Table Frame Data RateLength Target Error (bps) (ms) Coding Nominal_Attribute_GainPilot_Reference_Level Rate¹ 1,200 80 Convolutional −56 0 0.05 1,350 40Convolutional −54 0 0.05 1,500 20 Convolutional −47 0 0.01 1,800 20Convolutional −42 3 0.01 1,800 40 or 80 Convolutional −45 3 0.05 2,40040 or 80 Convolutional −30 0 0.05 2,700 20 Convolutional −22 0 0.013,600 20 Convolutional −13 3 0.01 3,600 40 or 80 Convolutional −17 30.05 4,800 20 Convolutional −2 0 0.01 4,800 40 or 80 Convolutional −3 00.05 7,200 20 Convolutional 15 3 0.01 7,200 40 or 80 Convolutional 10 30.05 9,600 20 Convolutional 30 0 0.01 9,600 40 or 80 Convolutional 24 00.05 9,600  5 Convolutional 58 0 0.01 (RC 3 and 5) 9,600  5Convolutional 54 3 0.01 (RC 4 and 6) 14,400 20 Convolutional 44 3 0.0114,400 40 or 80 Convolutional 40 3 0.05 19,200 20, 40, or 80Convolutional 50 1 0.05 28,800 20, 40, or 80 Convolutional 56 11 0.0538,400 20, 40, or 80 Convolutional 60 11 0.05 57,600 20, 40, or 80Convolutional 72 18 0.05 76,800 20, 40, or 80 Convolutional 72 21 0.05115,200 20, 40, or 80 Convolutional 80 32 0.05 153,600 20, 40, or 80Convolutional 84 36 0.05 230,400 20 or 40 Convolutional 88 46 0.05259,200 80 Convolutional 96 50 0.05 307,200 20 or 40 Convolutional 96 540.05 460,800 20 Convolutional 104 61 0.05 518,400 40 Convolutional 10464 0.05 614,400 20 Convolutional 112 68 0.05 1,036,800 20 Convolutional128 83 0.05 4,800 80 Turbo 2 0 0.05 7,200 80 Turbo 24 0 0.05 9,600 40 or80 Turbo 34 0 0.05 14,400 40 or 80 Turbo 42 0 0.05 19,200 20, 40, or 80Turbo 44 2 0.05 28,800 20, 40, or 80 Turbo 52 9 0.05 38,400 20, 40, or80 Turbo 56 10 0.05 57,600 20, 40, or 80 Turbo 64 19 0.05 76,800 20, 40,or 80 Turbo 68 19 0.05 115,200 20, 40, or 80 Turbo 76 29 0.05 153,60020, 40, or 80 Turbo 76 33 0.05 230,400 20 or 40 Turbo 88 39 0.05 259,20080 Turbo 88 48 0.05 307,200 20 or 40 Turbo 88 50 0.05 460,800 20 Turbo104 54 0.05 518,400 40 Turbo 108 56 0.05 614,400 20 Turbo 112 58 0.051,036,800 20 Turbo 125 78 0.05 ¹The error rate is the frame error ratewhen a single transmission unit is used; otherwise, the LogicalTransmission Unit (LTU) error rate is used. This applies to the cases inwhich the Target Error Rate is 0.05.

What is claimed is:
 1. A method of determining priority of a station,comprising: determining, by an apparatus, pilot energy over noise plusinterference ratio (Ecp/Nt); determining, by the apparatus, a softhandoff factor (SHOfactor); determining, by the apparatus, a fairnessvalue (F); determining, by the apparatus, a fairness factor α; anddetermining, by the apparatus, priority of the station based on thepilot energy over noise plus interference ratio, the soft handofffactor, the fairness value, and the fairness factor α.
 2. The method ofclaim 1, wherein determining the soft handoff factor is based on averagereceived pilot powers.
 3. The method of claim 1, wherein the fairnessvalue is a proportional fairness value.
 4. The method of claim 1,wherein the fairness value is a round robin fairness value.
 5. Themethod of claim 3, wherein determining the proportional fairness valueis based on a ratio of a maximum requested rate to an averagetransmission rate.
 6. The method of claim 5, wherein determiningpriority of the station w_(i) is based on:$w_{i} = {\frac{1}{{Ecp}/{{Nt}_{i}({SHOfactor})}} \cdot {({PF})^{\alpha}.}}$7. An apparatus for determining priority of a station, comprising: meansfor determining pilot energy over noise plus interference ratio(Ecp/Nt); means for determining a soft handoff factor (SHOfactor); meansfor determining a fairness value (F); means for determining a fairnessfactor α; and means for determining priority of the station based on thepilot energy over noise plus interference ratio, the soft handofffactor, the fairness value, and the fairness factor α.
 8. The apparatusof claim 7, wherein the soft handoff factor is based on average receivedpilot powers.
 9. The apparatus of claim 7, wherein the fairness value isa proportional fairness value.
 10. The apparatus of claim 7, wherein thefairness value is a round robin fairness value.
 11. The apparatus ofclaim 9, wherein the proportional fairness value is based on a ratio ofa maximum requested rate to an average transmission rate.
 12. Theapparatus of claim 11, wherein priority of the station w_(i) is basedon:$w_{i} = {\frac{1}{{Ecp}/{{Nt}_{i}({SHOfactor})}} \cdot {({PF})^{\alpha}.}}$13. A non-transitory computer-readable medium comprising instructionsstored therein, which when executed by a processor, cause the processorto perform operations comprising: determining pilot energy over noiseplus interference ratio (Ecp/Nt); determining a soft handoff factor(SHOfactor); determining a fairness value (F); determining a fairnessfactor α; and determining priority of the station based on the pilotenergy over noise plus interference ratio, the soft handoff factor, thefairness value, and the fairness factor α.
 14. The non-transitorycomputer-readable medium of claim 13, wherein determining the softhandoff factor is based on average received pilot powers.
 15. Thenon-transitory computer-readable medium of claim 13, wherein thefairness value is a proportional fairness value.
 16. The non-transitorycomputer-readable medium of claim 13, wherein the fairness value is around robin fairness value.
 17. The non-transitory computer-readablemedium of claim 15, wherein determining the proportional fairness valueis based on a ratio of a maximum requested rate to an averagetransmission rate.
 18. The non-transitory computer-readable medium ofclaim 17, wherein determining priority of the station w_(i) is based on:$w_{i} = {\frac{1}{{Ecp}/{{Nt}_{i}({SHOfactor})}} \cdot {({PF})^{\alpha}.}}$19. An apparatus for determining priority of a station, comprising: aprocessor configured to determine pilot energy over noise plusinterference ratio (Ecp/Nt), to determine a soft handoff factor(SHOfactor), to determine a fairness value (F), to determine a fairnessfactor α, and to determine priority of the station based on the pilotenergy over noise plus interference ratio, the soft handoff factor, thefairness value, and the fairness factor α.
 20. The apparatus of claim19, wherein the soft handoff factor is based on average received pilotpowers.
 21. The apparatus of claim 19, wherein the fairness value is aproportional fairness value.
 22. The apparatus of claim 19, wherein thefairness value is a round robin fairness value.
 23. The apparatus ofclaim 21, wherein the proportional fairness value is based on a ratio ofa maximum requested rate to an average transmission rate.
 24. Theapparatus of claim 23, wherein priority of the station w_(i) is basedon:$w_{i} = {\frac{1}{{Ecp}/{{Nt}_{i}({SHOfactor})}} \cdot {({PF})^{\alpha}.}}$